Catalyst for production of aromatic hydrocarbons and process for production of aromatic hydrocarbons using same

ABSTRACT

The catalyst is an L-type zeolite with platinum supported thereon, which is then treated with a halogen-containing compound. The catalyst has a long catalyst life and is extremely useful for the preparation of aromatic hydrocarbons from aliphatic hydrocarbons. The process using the catalyst provides a production of aromatic hydrocarbons with a high yield.

This is a division of application Ser. No. 07/341,386 filed Apr. 21,1989, now U.S. Pat. No. 05,091,251.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a catalyst for the production ofaromatic hydrocarbons and a process for the production of aromatichydrocarbons using the same and, more particularly, to such a catalystproducing the aromatic hydrocarbons with a high yield and having a longcatalyst life and to a process for the preparation of the aromatichydrocarbons with a high yield.

2. Description of Related Art

As processes for the production of aromatic hydrocarbons from aliphatichydrocarbons using a zeolite catalyst, there are known various processesincluding a process using as a catalyst a strongly acid zeolite such asZSM-5 as disclosed in Japanese Patent Kokoku Nos. 42,639/1981 and23,368/1983 as well as in Japanese Patent Kokai Nos. 92,717/1978 and140,934/1981; a process using a basic catalyst with platinum supportedthereon as disclosed in Japanese Patent Kokoku No. 57,408/1983 as wellas in Japanese Patent Kokai Nos. 80,333/1984, 133,835/1983 and22,614/1983; a process using as a catalyst an oxychlorinated L-typezeolite with a noble metal supported thereon as disclosed in JapanesePatent Kokai No. 168,539/1985; a process using as a catalyst acrystalline aluminosilicate with platinum or a fluoride supportedthereon as disclosed in Japanese Patent Kokoku No. 16,781/1975; aprocess for reaction in the presence of a halogen compound using as acatalyst a X-type, y-type or L-type zeolite with a metal of the VIIIgroup of the periodic table supported thereon as disclosed in JapanesePatent Kokai No. 15,489/1985; and a process using a catalyst in whichplatinum is supported on an L-type zeolite treated with ahalogen-containing compound, as disclosed in U.S. Pat. Nos. 4,681,865and 4,761,512.

The process using the strongly acid zeolite catalyst suffers from thedisadvantages that a large quantity of decomposed gases are caused tooccur and a yield of aromatic components is very low. The process usingthe basic catalyst with the platinum supported thereon offers theproblems with a low activity and with a short catalyst life although itcan provide a high yield of aromatic components. All the other priorprocesses present various problems in that some are insufficient intheir yield of aromatic components and other have a short catalyst life.

Other conventional processes using catalysts likewise may suffer fromthe disadvantages in that a yield aromatic components is low and/or thecatalyst life is short or present the difficulty that steps forpreparing the catalyst are complex.

SUMMARY OF THE INVENTION

In order to overcome the problems and disadvantages inherent in theconventional catalysts and processes using such catalysts, extensivestudies have been made to develop a catalyst capable of producingaromatic components with a higher yield and having a longer catalystlife than conventional ones and, at the same time, to provide a processfor efficiently preparing the aromatic components using such a catalyst.As a result, it has been found that a catalyst obtainable by treating anL-type zeolite with platinum supported thereon by a halogen-containingcompound can efficiently produce an aromatic component from ahydrocarbon selected from one member or more of a paraffin hydrocarbon,an olefin hydrocarbon, an acetylene hydrocarbon, a cyclic paraffinhydrocarbon and a cyclic olefin hydrocarbon.

Therefore, the present invention has the object to provide a catalystwhich is produced by treating the platinum-supporting L-type zeolitewith the halogen-containing compound and another object to provide aprocess for preparing the aromatic hydrocarbon using the catalyst.

In order to achieve the object, the present invention consists of acatalyst comprising an L-type zeolite with platinum supported thereon,which in turn is treated with a halogen-containing compound.

Furthermore, in order to achieve the another object, the presentinvention consists of a process for preparing an aromatic hydrocarbonwhich comprises the step of bringing one or more hydrocarbons selectedfrom a paraffin hydrocarbon, an olefin hydrocarbon, an acetylenehydrocarbon, a cyclic paraffin hydrocarbon and a cyclic olefinhydrocarbon into contact with a catalyst obtained by treating theplatinum-supporting L-type zeolite with a halogen-containing compound.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent in the course of the description of the preferredembodiments which follows, when considered in light of the accompanyingdrawings, in which:

FIGURE is a graph showing a variation in yields of aromatic hydrocarbonswhen operated for a long period of time using the catalyst according tothe present invention compared with conventional catalysts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The catalyst according to the present invention comprises L-type zeolitewith platinum supported thereon, which in turn is treated with ahalogen-containing compound.

The L-type zeolite may be represented by empirical formula:

    0.9-1.3M.sub.2/n.Al.sub.2 O.sub.3.5.0-7.0SiO.sub.2.0-9H.sub.2 O

(in which M is an alkali metal atom or an alkaline earth metal atom andn is an atomic valency of M)

and may be prepared from a starting material such as silica sol andpotassium aluminate or silica sol, potassium aluminate potassiumhydroxide and sodium hydroxide. Examples of such zeolite are disclosedin Japanese Patent Kokai Nos. 133,835/1983 and 80,333/1984.

The L-type zeolite is then supported with platinum. The platinum to besupported may be any kind of platinum. A source of platinum may include,for example, tetraamminplatinum chloride, chloroplatinic acid,chloroplatinate, hydroxytetraamminplatinum and dinitrodiaminoplatinum.An amount of the platinum to be supported on the zeolite is notrestricted to a particular one and may range generally from 0.1% to 5.0%by weight, preferably from 0.3% to 1.5% by weight, as translated intoplatinum, with respect to the total weight of the catalyst. The platinummay be supported on the L-type zeolite in any appropriate manner, forexample, such as vacuum impregnation, atmospheric impregnation,immersion, ion exchange and other techniques.

The L-type zeolite with platinum supported thereon is then treated witha halogen-containing compound. The halogen-containing compound mayinclude, for example, a fluorine-containing compound, achlorine-containing compound, a bromine-containing compound, aniodine-containing compound as well as a chlorine- andfluorine-containing compound. Preferred are the fluorine-containing andchlorine-containing compounds and more preferred is thefluorine-containing compound.

The fluorine-containing compounds may include a fluorohydrocarbon, or aso-called furone gas (Freon), and fluorochlorohydrocarbon, includingtrichloromonofluoromethane (CFCl₃) (Freon 11), dichlorodifluoromethane(CF₂ CL₂) (Freon 12), monochlorotrifluoromethane (CF₃ Cl) (Freon 13).dichloromonofluoromethane (CHFCl₂) (Freon 21), monochlorodifluoromethane(CHF₂ Cl) (Freon 22), trifluoromethane (CHF₃) (Freon 23).tetrafluoromethane (CF₄) (Freon 14),1,1,2-trichloro-1,2,2-trifluoroethane (CF₂ CICFCl₂) (Freon 113) and1,2-dichloro-1,1,2,2-tetrafluoroethane (CF₂ ClCF₂ Cl) (Freon 114).

The chlorine-containing compounds may be a chlorinated hydrocarbonincluding, for example, carbon tetrachloride (CCl₄), chloroform (CHCl₃),dichloromethane (CH₂ Cl₂), hexachloroethane (C₂ Cl₆), tetrachloroethane(C₂ H₂ Cl₄) and dichloroethane (C₂ H₄ Cl₂).

Reaction conditions for treatment of the L-type zeolite with platinumsupported thereon with the halogen-containing compound are notrestricted to particular ones and may be selected in accordance withsituations. For example, the platinum-supporting zeolite may be broughtinto contact with the catalyst at a temperature ranging from 80° C. to600° C. for a reaction time ranging from 1 minute to 20 hours.Preferably from 10 minutes to 2 hours. If the halogen-containingcompound is used in a gaseous form, the L-type zeolite may be exposed atthe above temperature for the above reaction time to ambient atmospherein which the halogen-containing compound is present in a gaseous form.

The catalyst thus prepared may be used for the production of an aromatichydrocarbon from a variety of hydrocarbons with a higher yield underappropriate reaction conditions. The process using the catalyst inaccordance with the present invention permits a production of thearomatic hydrocarbon with an extremely high efficiency.

The feedstock for the process according to the present may include aparaffin hydrocarbon, an olefin hydrocarbon, an acetylene hydrocarbon, acyclic paraffin hydrocarbon, a cyclic olefin hydrocarbon and a mixturethereof.

The paraffin hydrocarbon may be an aliphatic saturated hydrocarbonhaving from 6 to 10 carbon atoms and may include, for example, n-hexane,methylpentane, n-heptane, methylhexane. dimethylpentane, n-octane or thelike.

The olefin hydrocarbon may be an aliphatic unsaturated hydrocarbonhaving from 6 to 10 carbon atoms and may include, for example, hexene,methylpentene, heptene, methylhexene, dimethylpentene, octene or thelike.

The acetylene hydrocarbon may be an unsaturated hydrocarbon having from6 to 10 Carbon atoms and may include, for example, hexyne, heptyne,octyne or the like.

The cyclic paraffin hydrocarbon may be a cyclic saturated hydrocarbonhaving from 6 to 10 carbon atoms and may include, for example,methylcyclopentane, cyclohexane, methylcyclohexane. dimethylcyclohexaneor the like.

The cyclic olefin hydrocarbon may be a cyclic unsaturated hydrocarbonhaving from 6 to 10 carbon atoms and may include, for example.methylcyclopentene, cyclohexene, methylcyclohexene, dimethylcyclohexeneor the like.

The process according to the present invention proceeds upon exposure ofthe hydrocarbon as the feedstock to the catalyst under reactionconditions which are not restricted to particular ones. The temperatureis in the range generally from 350° C. to 600° C., preferably from 400°C. to 550° C. , and the pressure is in the range generally from 0 to 30kg/cm² G, preferably from 5 to 15 kg/cm² G. A WHSV may range generallyfrom 0.1 to 10 hour⁻⁵, preferably from 1 to 5 hour⁻¹. A supply ofhydrogen gas during reaction in a molar ratio of hydrogen gas to feedoil ranging from 1-to-1 to 20-to-1 can produce a better result.

The catalyst according to the present invention has a longer catalystlife and a higher activity and can produce various aromatic hydrocarbonsfrom various hydrocarbons with a higher yield. Thus the catalyst isextremely useful for the production of the aromatic hydrocarbons.

The process according to the present invention can provide the aromatichydrocarbons with a yield virtually as high as 70%, in some cases ashigh as approximately 90%, when the saturated hydrocarbon is used as afeedstock. Furthermore, the process can be conveniently operatedcontinuously for a long Period of time without a substantial reductionin high production yields because the catalyst can maintain its highlycatalytic activity for a long period of time. Furthermore, the treatmentwith the halogen-containing compound can be carried out in a hydrocarbonreforming reactor, and this treatment is advantageous for the productionof the catalyst.

Thus the present invention can be effectively utilized in a wide rangeof petrochemical fields in which aromatic hydrocarbons are produced andpetroleum fields in which high octane value fuels are prepared.

The present invention will be described more in detail by workingexamples as compared with comparative examples.

EXAMPLE 1

A silica-bound L-type zeolite (average particle size, 0.5 mm; Trade mark"TSZ-500" (produced by TOSO K.K.; 83% by weight) was impregnated with asolution of tetraamminplatinum dichloride [Pt(NH₃)₄ Cl₂ ] containing theplatinum in the amount of 0.5% by weight in an amount of a deionizedwater corresponding to a saturated water content of zeolite. After theplatinum was supported thereon, the platinum supporting L-type zeolitewas dried at 80° C. over a period of 3 hours by a hot air dryer. Thezeolite (15 grams) was then packed in a quartz reaction tube having theinner diameter of 20 mm and heated at 500° C. for 1 hour while nitrogenwas passed therethrough. Thereafter nitrogen gas was changed tomonochlorotrifluoromethane (CF₃ Cl) and the reaction was carried out at450 for 2 hours in an atmosphere of CF₃ Cl. Then CF₃ Cl was changedagain to nitrogen gas and the temperature was returned to roomtemperature. The resulting platinum-supporting L-type zeolite(hereinafter referred to as "Catalyst 1") was found to contain 0.56% byweight of fluorine and 0.58% by weight of chlorine.

EXAMPLE 2

The platinum-supporting L-type zeolite (5 grams) obtained by drying theL-type zeolite impregnated with platinum was packed in a quartz reactiontube having the inner diameter of 20 mm and heated to 150° C. whilenitrogen gas is flown thereinto. After the temperature reached 150° C.,carbon tetrachloride was supplied into the nitrogen gas by a pump toamount to the concentration of 2%. After 1 hour, the supply of carbontetrachloride was suspended and the temperature in the reaction tube wasdropped to room temperature while nitrogen gas was flown thereinto. Theresulting platinum-supporting L-type zeolite (hereinafter referred to as"Catalyst 2") was found to contain chlorine 1.7% by weight.

EXAMPLE 3

The procedures of Example 1 were followed in substantially the samemanner with the exception that the halogen-containing compound waschanged from monochlorotrifluoromethane to difluorodichloromethane andthe temperature for treatment with the halogen-containing compound waschanged to 350° C., thus yielding a platinum-supporting L-type zeolite(hereinafter referred to as "Catalyst 3").

EXAMPLE 4

The procedures of Example 2 were followed in substantially the samemanner with the exception that the halogen-containing compound waschanged from monochlorotrifluoromethane to 1,2-dichloroethane, thusyielding a platinum-supporting L-type zeolite (hereinafter referred toas "Catalyst 4").

COMPARATIVE EXAMPLE 1

The procedures of Example 1 were followed in substantially the samemanner with the exception that no treatment with the halogen-containingcompound was carried out, thus yielding a platinum-supporting L-typezeolite (hereinafter referred to as "Catalyst 5").

EXAMPLE 5

A conversion reaction of n-hexane was carried out using Catalyst 1.Catalyst 1 (0.5 grams) was packed in a quartz reaction tube and heatedto 540° C. while hydrogen gas was blown thereinto and subjected toreduction for 24 hours. A raw material was then fed to the reaction tubein molar ratio of hydrogen to n-hexane of 5 to 1 at a WHSV of 2.0 hour⁻¹and reacted at 500° C. and atmospheric pressure. The relationship ofreaction times with yields of aromatic hydrocarbons is shown in FIGURE.

COMPARATIVE EXAMPLE 2

The procedures of Example 5 were followed in substantially the samemanner with the exception that Catalyst 5 was substituted forCatalyst 1. The relationship of reaction times with reaction yields ofaromatic components is shown in FIGURE.

EXAMPLES 6-9

The procedures of Example 5 were followed in substantially the samemanner with the exception that Catalysts 1 to 4 were used in place ofCatalyst 1, respectively, the reaction was carried out at 420° C. andreduction with hydrogen gas was done at 520° C. for 3 hours.

Results obtained after a 5-hour reaction is shown in Table 1 below.

COMPARATIVE EXAMPLE 3

The procedures of Example 5 were followed in substantially the samemanner with the exception that Catalyst 5 was used.

Results are shown in Table 1 below.

                  TABLE 1                                                         ______________________________________                                                                   COMPAR-                                                      EXAMPLES         ATIVE                                                        6     7       8      9     EX. 3                                    ______________________________________                                        Catalyst No.                                                                              1       2       3    4     5                                      Conversion (% wt)                                                                         76.7    82.0    72.5 79.1  62.2                                   Selectivity (% wt)                                                                        96.5    96.0    96.1 96.3  95.2                                   Aromatic Compds                                                                           74.0    78.7    69.7 76.2  59.2                                   (Yield, % wt)                                                                 ______________________________________                                         Notes:                                                                        Conversion (% by weight) = yield of aromatic components + yield of            hydrocarbon components having from 1 to 5 carbon atoms                        Selectivity (% by weight) = [yield of aromatic components/(yield of           aromatic components + yield of hydrocarbon components having from 1 to 5      carbon atoms)] × 100                                               

EXAMPLES 10-11

The procedures of Example 5 were followed in substantially the samemanner with the exception that Catalysts 1 and 2 were used,respectively, and the reaction was carried out under pressure of 5kg/cm² using hydrocarbons as a feedstock as shown in Table 2 below.

Results are shown in Table 3 below.

COMPARATIVE EXAMPLE 4

The procedures of Example 10 were followed in substantially the samemanner with the exception that Catalyst 5 was used.

Results are shown in Table 3 below.

                  TABLE 2                                                         ______________________________________                                        Kinds of Hydrocarbons                                                                           Rate (% wt)                                                 ______________________________________                                        2,3-Dimethylbutane                                                                              2.6                                                         2-Methylpentane   23.3                                                        3-Methylpentane   16.7                                                        n-Hexane          49.3                                                        Methylcyclopentane                                                                              8.1                                                         ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                                                COMPAR-                                                             EXAMPLES  ATIVE                                                             10       11     EX. 4                                             ______________________________________                                        Catalyst No.  1          2      5                                             Conversion (% wt)                                                                           98.2       97.5   97.8                                          Selectivity (% wt)                                                                          85.9       81.5   80.3                                          Aromatic Compds                                                                             84.4       79.5   78.5                                          (Yield, % wt)                                                                 ______________________________________                                    

What is claimed is:
 1. A process for preparing an aromatic hydrocarboncomprising exposing one or more hydrocarbons selected from the groupconsisting of a paraffin hydrocarbon, an olefin hydrocarbon, a cyclicparaffin hydrocarbon and a cyclic olefin hydrocarbon to a catalystcomprising an zeolite having a structure of an L-zeolite with platinumsupported thereon, said catalyst being prepared by supporting theplatinum on the zeolite having a structure of an L-zeolite, and treatingthe platinum and zeolite with a halogen-containing compound.
 2. Aprocess as claimed in claim 1, wherein an amount of platinum supportedthereon ranges from 0.1% to 5.0% by weight on the basis of the totalweight of the catalyst.
 3. A process as claimed in claim 1, wherein thehalogen-containing compound is a fluorine-containing compound.
 4. Aprocess as claimed in claim 1, wherein the halogen-containing compoundis a chlorine-containing compound.
 5. A process is claimed in claim 1,wherein the halogen-containing compound is a fluorine- andchlorine-containing compound.
 6. A process as claimed in claim 1,wherein the halogen-containing compound is monochlorotrifluoromethane,difluorodichloromethane or 1,2-dichloroethane.
 7. A process as claimedin claim 1 wherein a hydrocarbon is exposed at a temperature rangingfrom 350° C. to 800° C., a pressure ranging from 0 to 30 Kg/cm² G and aspace velocity (WHSV) ranging from 0.1 to 10 hour⁻¹, to a catalystcomprising a platinum supported on a zeolite having the structure of ofL-zeolite, and treating said zeolite with a halogen-containing compound.